The present invention relates to seals or packings used for preventing escape of gas or liquid through or from structural closures, more particularly to gaskets used for preventing such escape through or from manually-operated movable door-like closures.
Naval vessels are frequently designed to contain one or more watertight/airtight, quick-acting, individual-acting movable structural closures, such as doors, hatches and scuttles, which selectively permit or deny passage between locations or compartments.
Noteworthy among gasket designs which the U.S. Navy has utilized for purposes of sealing such closures is the "MIL-R-900" gasket. The MIL-R-900 gasket has been serviceable but has been considered neither problem-free nor performance-optimal.
The MIL-R-900 material has tended to develop permanent set in the gasket, thereby negating all or vitually all watertight/airtight qualities of the gasket. The MIL-R-900 gaskets have been changed out approximately every six months due to permanent set, deterioration from ultraviolet degradation, drying out and damage.
Installation of the MIL-R-900 gasket has averaged about 2.5 hours and recovery time (for allowing the gasket to recover from the installation process prior to finish cut and testing) has averaged about 24 hours; hence, utilization of the MIL-R-900 gasket has proven to be labor-intensive.
An additional concern for the U.S. Navy has been the ability of a gasket to withstand fire and concomitant high temperatures and toxic fumes aboard vessels, e.g., at shipboard firezone boundaries. The U.S. Navy has been using the "MIL-G-17927" gasket, specificially designed for firezone boundaries, which costs about $15 to $20 per foot for the U.S. Navy to procure, significantly more expensive than the $.50 to $1 per foot MIL-R-900 standard gasket.